Remove potentially expensive check in ForestMerge.

law/contrib/tasks/__init__.py

@@ -210,10 +210,6 @@ def __init__(self, *args, **kwargs):
         self._merge_forest = None
         self._leaves_per_tree = None
 
-        # the merge factor should not be 1
-        if self.merge_factor == 1:
-            raise ValueError("merge factor must not be 1")
-
         # modify_param_values prevents the forest from being a workflow, but still check
         if self.is_forest() and self.is_workflow():
             raise Exception("merge forest must not be a workflow, {} misconfigured".format(self))